Let me the agnostic take a stab at this from a distance....
She is in jail, not rehab so it is doubtful she is getting support for her addiction issues. Jail is not rehab. Sounds like you are trying to fill that role as rehab counselor of some sort and to me, if I were her parent, I'd be wary as well. Because she is fragile and seems hungry for answers to her predicament, she will probably listen to anyone who came up to her, good intentions or not.
As harsh as it is for you to experience, and no one knows dad's motives or thoughts but just on the surface, I think maybe you are ovestepping your role from friend to 'counselor' and without training, that would make me as a parent suspicious.
Just my feedback from what you wrote....